Method and apparatus for forward power control in a communication system

Abstract

In a data communication system capable of variable rate transmission, the data rate is determined by the largest C/I measurement of the forward link signals as measured at the Access Terminal. In one embodiment, the data transmission is scheduled based on an Access Terminal initiated forward power control, which reduces forward link rate quantization loss due to excess transmit power. The Access Terminal reports to the Access Point the excess C/I estimate for the selected rate. The Access Point then reduces its transmit power by an appropriate amount when serving that Access Terminal. In another embodiment, the data transmission is scheduled based on an Access Point initiated forward power control. The Access Point varies its transmit power over time either randomly or in synchronism with neighboring Access Points in the communication system, which enables an increase in the throughput achieved by users that receive a significant amount of interference.

1. A method for packet data transmission from at least one Access Point to an Access Terminal comprising:
 receiving data request messages from a plurality of Access Terminals; 
 calculating an average served rate for each of the plurality of Access Terminals; 
 calculating a ratio of requested data rate to the average served rate for each of the plurality of Access Terminals; 
 scheduling a transmission of data from the Access Terminal having the highest ratio of requested data rate to average served rate; and 
 transmitting data from said selected Access Point at a randomly varying transmit power in accordance with said data request message. 
 
   
   
     2. The method of  claim 1 , wherein the ratio is calculated as: DRC I (n)/R I (n), where R I (n)=(1−1/tc)*R I (n−1)+(1/tc); DRC I (n) is the requested data rate of Terminal I at a slot n; RI(n) is the average served rate in a slot n−1 to I; and tc is a scheduler time constant. 
   
   
     3. A method for packet data transmission from at least one Access Point to an Access Terminal in a communication system, comprising:
 receiving data request messages from a plurality of Access Terminals; 
 calculating an average served rate for each of the plurality of Access Terminals; 
 calculating a ratio of requested data rate to the average served rate for each of the plurality of Access Terminals; 
 biasing a schedule of a transmission of data from the Access Terminal based on the ratio of requested data rate to average served rate; and 
 transmitting data from said selected Access Point at a transmit power in synchronism with neighboring Access Points in the communication system in accordance with said data request message. 
 
   
   
     4. A method for packet data transmission from at least one Access Point to an Access Terminal in a communication system, comprising:
 receiving data request messages from a plurality of Access Terminals; 
 calculating an average served rate for each of the plurality of Access Terminals; 
 calculating a ratio of requested data rate to the average served rate for each of the plurality of Access Terminals; 
 scheduling a transmission of data from the Access Terminal having the highest ratio of requested data rate to average served rate; and 
 transmitting data from said selected Access Point at a transmit power in synchronism with neighboring Access Points in the communication system in accordance with said data request message. 
 
   
   
     5. The method of  claim 4 , wherein the transmit power is at a maximum depends on the Access Point's boresite azimuth angle. 
   
   
     6. The method of  claim 5 , wherein the transmit power
     P ( t )= P   0 (dBm)+∂(dB)*Cos(2 *π*t/T −θ) where, 
 P 0  is the Access Point nominal transmit power; 
 θ is the Azimuth angle; 
 T is the time to scan 360°; and 
 ∂=peak in dB. 
 
   
   
     7. An Access Point, comprising:
 a means for receiving data request messages from a plurality of Access Terminals; 
 a means for calculating an average served rate for each of the plurality of Access Terminals; 
 a means for calculating a ratio of requested data rate to the average served rate for each of the plurality of Access Terminals; 
 a means for scheduling a transmission of data from the Access Terminal having the highest ratio of requested data rate to average served rate; and 
 a means for transmitting data from said selected Access Point at a randomly varying transmit power in accordance with said data request message.